1Chemical signals in animalsKeywordsReading Ch. 45• Endocrine system• Hormone• Target cell• Steroid• Amino acid derived hormone• Surface receptors• Internal receptors• Action of steroids• Glucose homeostasis• Insulin• Glucagon• Epinephrine• Norepinephrine• ACTHChemical signals• Inside and outside an organism• What is a chemical signal? Generally involves highly specific receptor/signal bindinghttp://www.youtube.com/watch?v=Ms_ehUVvKKkPheromone – signal outside of organisms• A small often volatile chemical signal that functions in communication between animals• Periplanone – emitted by female American cockroaches• Human pheromones? Vomeronasal organ• http://www.youtube.com/watch?v=NhTlTLNkbUwWill focus on chemical signals inside organisms • Endocrine system• Nervous system (later lectures)2Hormone• Chemical signal secreted into body fluids (usually blood)• Effective in minute amounts• Plasma testosterone– 1.3 to 2.3 nanomoles per liter• Plasma glucose– 5 millimoles per liter• 2 to 4 million glucose molecules for every one testosteroneHow dilute is 1.3 nmoles per liter? • Ratio of water molecules to testosterone molecules is 43 billion to one• What is 43 billion?• There are 43 billion square feet in a square 40 miles x 40 milesMany types of molecules are used as hormones• Amino acid derived– Single amino acids– Peptides– Proteins– Glycoproteins• Steroid (lipid soluble)– Made from cholesterol– Include sex hormonesHormones act on specific target cells in two ways• Surface receptors• Within target cells (internal receptor)Surface receptor Internal receptor3Action of steroids• Binding of steroid to internal receptor• formation of complex that binds to DNA• Binding regulates gene expression• increases or decreases gene productAction of steroids (diagram not in notes; see fig 45.5 p. 898)Two examples of hormone action• Glucose homeostasis• Stress and the adrenal glandGlucose homeostasis• Homeostasis = The steady-state physiological condition of the body• Glucose = major fuel of cellular respiration• Normal blood glucose level = 5 millimolesper liter• How is this regulated?• First look at when glucose levels are too highP. 968• High blood glucose causes beta cells to release insulin4Summary• Beta cells release insulin• Insulin causes body cells and liver to take up glucose• Glucose levels restoredWhat happens if you need to increase blood glucose?• Low blood glucose causes alpha cells to release the hormone glucagon• Glucogon stimulates the liver to break down glycogen releasing glucoseSummary• Low blood glucose causes alpha cells to release the hormone glucagon• Glucogon stimulates the liver to break down glycogen releasing glucose5Glucose homeostasis• Example of use of amino-acid derived hormones: insulin and glucagon are peptides• Surface receptors on target cellsDiabetes mellitus• Greek = copious urine, honey• Type I - autoimmune disorder - cells of pancreas are targeted - no ability to produce insulin - usually occurs during childhood• Type II (90%) - reduced responsiveness of target cells or insulin deficiency-usually occurs after age 40Stress and the adrenal gland• Short-term response - Epinephrine (adrenaline) and norepinephrine• Long-term response - ACTH and corticosteroidsP. 971Short-term stress: medulla of the adrenal gland6Some effects of epinephrine and norepinephrine• Glycogen broken down to glucose• Increased blood pressure, breathing, metabolic rateLong-term stress: cortex of the adrenal glandCorticosteroids (mineral- and gluco- corticoids) released by adrenal cortex• Some effects: increased blood volume and blood pressure, breakdown of protein and fatsFinal thoughts: Do zebras experience stress?• Baboon studies• Wolf and mongoose studies• Practice questions• Steroid hormones are:– A. the primary hormones involved in glucose homeostasis– B. a class of hormones that include corticosteroids– C. unable do diffuse across membranes• Norepinephrine and epinephrine– A. Lower blood pressure– B. Are released by the hypothalamus– C. Are released by the adrenal medulla– D. Lower blood glucose• Corticosteroids are produced in response to:– A. Short term stress– B. Epinephrine release– C. ACTH– D. Elevated blood glucose• Insulin is released by– A. Pancreatic beta cells– B. Adrenal medulla– C. Adrenal cortex– D. Pituitary